Cisco and Italian ISP Messagenet will try to convince a European court today that it should overturn the EU's approval of Microsoft's acquisition of VoIP biz Skype.

The firms will attempt to get the Euro beaks to reverse the European Commission's clearance of the $8.5bn gobble in 2011 without any concessions. Networking giant Cisco and Messagenet claim there were "manifest errors" made when the EC originally came to the decision that the deal wasn't anticompetitive.

Cisco said last year that the legal action was not taken lightly and it was "about one thing only: securing standards-based interoperability in the video calling space".

“The industry recognises the need for ubiquitous unified communications interoperability, particularly between Microsoft/Skype and Cisco products, as well as products from other unified communications innovators," Marthin De Beer, Cisco veep, said on the corporate blog.

“Microsoft’s plans to integrate Skype exclusively with its Lync Enterprise Communications Platform could lock in businesses who want to reach Skype’s 700 million account holders to a Microsoft-only platform.”

In the court proceedings, the firms argue that the merger has led to a combined market share of more than 80 per cent in video call services on Windows-based PCs.

"Both the combination of powerful network effects accruing to the largest installed base of users and the merging company's full control of the Windows Operating System and other adjacent applications will reinforce the dominant position and eliminate any incentive which the merged entity may have to offer interoperability with competing products," they claim.

De Beer said that making a video-to-video call should be as easy as dialling a phone number.

"Today, however, you can't make seamless video calls from one platform to another, much to the frustration of consumers and business users alike," he said.

Cisco and fixed line and broadband firm Messagenet are appealing to the EU's General Court, but if they don't get the result they want there, they'll be able to take the case on to the European Court of Justice. ®